共振多光繞射在氧化鐵系統之研究

Resonant Multi-wave X-ray Diffraction study on Iron Oxides System

翁世璋(Shih-Chang Weng)

指導教授 ： 張石麟

國立清華大學/理學院/物理學系/博士(2009年)

https://doi.org/10.6843/NTHU.2009.00471

摘要

The Resonant X-ray Scattering(RXS) is one of the most used techniques to
study the strong-correlation systems. The same as usual RXS, the Resonant
Multi-wave X-ray Diffraction also provides the dispersion correction information.
Moreover, the multi-wave diffraction gives not only the intensity
information but also the phase information. In this dissertation, the resonant
multi-wave diffraction method is applied to investigate two iron oxide
systems, Fe2O3 and Fe3O4.

In the Fe2O3 system, or called hematite, the phenomenon of twice phase
inversion is observed in the iron K-edge and pre-edge. The resonant multiwave
diffraction calculation shows a consistent phase change as observed in
the the experiment.

In the Fe3O4, magnetite, there is an open question about the charge ordering
at low temperature. To study the charge disproportion on octahedral
sites Fe atoms, two series of three-wave diffraction profiles, (002)/(¯3
¯11) and (002)/(311), are measured in the iron K-edge resonant region. The resonant
multi-wave diffraction spectrum is in agreement with the charge-ordering
calculation, and the charge disproportion is close to 2.9+ and 2.1+.

關鍵字

共振繞射 ； X光繞射 ； 複繞射 ； 氧化鐵

並列摘要

共振X光繞射(Resonant X-ray Sscattering;　RXS)是研究強相關系統最為普
及的一種技術。如同RXS一般，共振多光繞射亦提供色散修正(Dispersion
correction)資訊。此外，共振多光繞射不僅提供強度資訊，也提供了相位
資訊。在此篇論文中，乃應用共振多光繞射方法於探究兩種鐵氧化物系
統—Fe2O3及Fe3O4。
在Fe2O3系統(即所謂的Hematite)中，在鐵的K吸收邊及前吸收邊內，
可觀察到兩次相位反轉之現象。共振多光繞射計算顯示出與實驗一致之相
位變化。
於Fe3O4系統中，其低溫下的電荷有序結構(Charge Ordering)仍為未解
的問題。為了研究八面體鐵原子上的電荷不對稱性，我們量測(002)/(¯3
¯11) 與(002)/(311) 兩組三光繞射在鐵K 吸收邊之強度變化。多光共振繞射的
實驗結果顯示出低溫下的電荷有序結構， 而其電荷不對稱性為：2.9+ 與
2.1+。

並列關鍵字

resonant x-ray scattering ； x-ray diffraction ； Fe3O4 ； Fe2O3 ； Hematite ； Magnatite

參考文獻

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